1. Field of the Invention
The present invention relates to an electronic device.
2. Description of the Prior Art
An anti-magnetic watch is defined in JIS B7024 xe2x80x9cAnti-magnetic watchesxe2x80x9d. This definition is made to specify a timepiece whose time does not stray when the watch is erroneously placed on a magnetism generating product.
A conventional watch is shown in FIG. 5. To an upper portion of a case side wall 20 defining a through-hole in its center portion, a decorative bezel 10 having an inner diameter smaller than the through-hole is pushed and fitted in the through-hole with a gasket 30 between the two. A glass 6 is fitted to the upper portion of the decorative bezel 10 with a gasket 40 between the two. A movement 7 with a dial 5 is inserted into this space. A part of upper face of the dial 5 contacts with a stepped portion of the decorative bezel 10 and, if the case back lid is closed, the movement 7 is fixed by a casing ring (not shown) which pushes up the movement 7.
In the case back lid 1, a soft magnetic material is fixed to the movement side by an adhesive 3, etc. so as to provide the antimagnetic protection. On this occasion, it is necessary to cover a direction susceptible to a magnetic force (refer to Japanese Patent Application JP-A-5-295247 and Japanese Patent Application JP-A-6-106901).
Since the portion of a timepiece body (movement), susceptible to magnetic force is covered with the soft magnetic material in this conventional art, it is shielded from external magnetism. Incidentally, in order to additionally improve the antimagnetic protection, a separate soft magnetic material part is adhered to the back face of the dial 7 (refer to Japanese Patent. Application JP-A-10-3229462).
However, if the soft magnetic material is adhered to the case back lid in order to satisfy the antimagnetic performance, the conventional watch cannot withstand the test of JIS B7021 xe2x80x9cWaterproof watches for general usexe2x80x94Kinds and performancesxe2x80x9d or JIS B7024 xe2x80x9cWaterproof watches for divingxe2x80x94Kinds and performancesxe2x80x9d. In order to ensure waterproof protection, material strength which withstands underwater pressure and does not damage the timepiece main body (movement) is required. For this reason, an timepiece case back armor layer which can withstand the pressurized waterproof test, a soft magnetic material layer which is necessary for the antimagnetic protection, and additionally a holding layer comprising adhesive, etc. for adhering, is required.
Further, if the soft magnetic material is applied directly to the case back, it is causes problems because it is liable to rust and it is difficult to attain a polished surface.
Thus for the above reasons, in the conventional method of adhering the soft magnetic material, the total thickness of the antimagnetic watch is great, which is a great problem when wearing ease and attractive shape are desired.
A timepiece of the present invention has a case containing a movement and a case back lid which is fixed to the case side wall, the case back lid comprising a clad material of two-layers, a soft magnetic material and a non-magnetic material, the soft magnetic material portion disposed on the movement side.
Another timepiece of the present invention has a case containing a movement and a case back lid-which is fixed to the case side wall, the case back lid comprising a three-layer clad material in which a soft magnetic material is provided between a 1st non-magnetic material and a 2nd non-magnetic material.
In the timepiece of the present invention, it is preferable that the soft magnetic material is selected from the group consisting of: pure iron, silicon steel plate, permalloy and ferritic stainless steel.
In the timepiece of the present invention it is preferable that the non-magnetic material is austenitic stainless steel or titanium.
In the timepiece of the present invention, it is preferable that a thickness of the soft magnetic material is between 0.2 and 0.7 mm.
Further, in the timepiece of the present invention, the case back lid has a raised portion fixed to the case band, and the soft magnetic material is disposed on the inner side of the case back lid and includes the raised portion. The outside of the raised portion is the non-magnetic material and, by making its inside the soft magnetic material, it is possible to cover a wide area with the soft magnetic material without applying a rust prevention to the soft magnetic material.